Method for the flotation of ores



Patented June 11, 1940 UNITED STATES PATENT OFFICE T METHOD FOR THE FLOTATION OF ORES Emil Ott, New Castle, DeL, assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing. Original application July 10, 1937,

Serial No. 153,064. Divided and this application September .17, 1938, Serial No. 230,385

3 Claims. (crane-46s) This invention relates to a method for the I flotation of: ores and more particularly to a methetc., from the distillate.

This alkaline extract isfblown with steam to remove certain sulfur compounds, and allow it to .beused for the extraction of further distillates. The organicsulfur compounds separated in this way from the extract consisting of various alkyl Tmercaptaus and sulfides have heretofore been burned to get rid of them, and even in burning have given troublesome problem in the production of sulfur dioxide.

Now, in accordance withTthis invention, I have found that I can produce a. valuable reagent for use in the concentration of. minerals Tby flotation processes by the treatment of this crude mixture of organic sulfur compounds with a free alkali metal, an alkali metal hydroxide or an alkali metal monoxide and with carbon disulfide. This treatment transforms the mixture of alkyl mercaptans present to alkyl trithiocarbonates. I am unaware as to the elfect of this treatment upon the other ingredients present in the mixture. However, contrary to expectation, sucha mixed product is valuable flotation reagent so the compounds themselves either do not have a deleterious eiiect on the flotation properties of the mixtures, or are themselves transformed into flotation reagents. Furthermore, the organic sulfides and other impurities which may be pres ent in such mixtures, or their reaction products,

do not interfere with the desirable appearance of the product, and do not detrimentally effect its stability. The latter is. surprising, and particularly important, since products of this type have a tendency to instability. 1 r

TItwill be appreciated that by means of my inventionI not only provide a valuable flotation reagent from material which has heretofore been substantially useless, but also avoid any complex refining procedures for the separation of the T alkyl mercaptans from other materials, such as, U sulfides, disulfidesf and: various complex sulfur compounds which may be present. In this way I provide a very economical and efllcientprocess for making a valuable flotation reagent.

The crude mixture which I treat contains,

along with the complex impurities, methyl mercaptan, propyl mercaptans, butyl mercaptans, ethyl mercaptan, and higher alkyl mercaptans,

in smaller amounts, and ordinarily boils within H the range of about 25 C. to about 170 C. How'- ever, the boiling range of the mixture used may be more narrow by simple distillation, giving fractions having a higher content of any one component. However, with the exception of the highly volatile methyl mercaptan, it is practically impossible to separate the individual mercaptans as pure compounds from such a complex crude mixture, due to the closeness of the boilingpoints of the various components. a

While methyl mercaptan occurs in such crude mixtures in substantial amounts, it is frequently desirable to reduce its amount in the mixture,

due to its pronounced and disagreeable odor. This may be readily accomplish'edat the refinery by adjustment of the conditions of condensation of the lnixture, or bydistilling it out of the mix-T ture before reaction to form the trithiocarbonate. In carrying out the method in accordance with this, invention I prefer to use substantially molecular proportions of alkali metal hydroxide, al- T kali metal, or alkalimetal monoxide, asthe case. may be, and carbon disulfide with anamount of the crude mixture which corresponds to the average molecular weight of the alkyl mercaptans present, or ahamount of the crude mixture slightly in excessjof the average molecular.

weight of the alkyl mercaptans present. In any case, itis desirable to carry" the reaction to completion" so that a minimum of free alkali metal hydroxide or alkali metal remains in the final product, since its presencetends to render the productfunstable.

The alkali metal hydroxide which I use may 7 be, for example, sodium hydroxide, potassiumhydroxide,lithiuni hydroxide, etc, and may be used either in the form of a solid or in aqueous solution. The alkali metal monoxide which I use may be, for example, sodium monoxidet potassium monoxide, lithium monoxide, etc., and will desirably be usedin the form of flakes or a, finely divided. powder to secure uniform and rapid re-,

action. When used in solid form, the alkali metal hydroxide will likewise: desirably be used alkali metals, however, present disadvantages in their high cost and in the danger attendant in handling them. When they are used, they will be substituted for equivalent quantities of the monoxides or hydroxides. It will be understood, however, that the use of alkali" metals, the monoxides and the hydroxides fall within the scope of my invention. It will also be understood that the products of the reaction of an alkali metal hydroxide, an alkali metal monoxide or a free alkali metal. are fully equivalent and are all within the scope of my invention.

In carrying out this reaction, it is desirable to avoid oxidizing conditions, since the product is sensitive in this respect, and hence I prefer to exclude any oxygen from the reaction mixture with anon-oxidizing gas, such as, for example, nitrogen, carbon disulfide, alkyl'mercaptans, etc.,

orunder vacuum in a closed system.

The temperature at which I carry out this reaction may be Within the range of about 0 C., to an upper limit set by the reflux temperature of the volatile ingredients of the reaction mixture. by. the reflux of the carbon disulfide or by the reflux temperature of the alkyl mercaptan mixture, depending'upon which boils at the lower temperature. I prefer to use a temperature within the range of about 0 C..to about 40 C.

In carrying out the method in accordance with -this invention the crude alkyl mercaptan mixture, the. alkali metal hydroxide and carbon di- ,r e acti on,- vessel in which thereactants can be sulfide'may be mixed in any desired order in a thoroughly. mixed, and which is provided with a reflux condenser and means for adequate cooling. Adequatecooling is desirable to prevent loss of the volatile ingredients by evaporation, and avoid thermal decomposition of the product; The reaction vessel Will desirably be flooded with inert gas when necessary to avoidoxidation of the product and any tendency to explosion.

When using an aqueous solution of an alkali :metalthydroxide for carrying out this reaction,

vthe-product may be recovered by precipitation from thereaction mixture, and the mother liquor remaining used as the reaction medium in a subsequent batch for the production of another lot of the material; thus, avoiding loss of the :product due to solution in the mother liquor. .-,W'hen the alkali metal, alkali metal hydroxide or alkali metal monoxide is used in solid form the product of the reaction will be found to be in solidform, and is useful in that form. without purification or separation of the ingredients.

-'-Although as much as one mole of water may be produced in the .reaction per mole of the reactants employed, this water need not be sepa- "rated from the product and does not in any way harm the product.

To further illustrate the methodin accordance with this invention,-I may cite the following examples: r

. well.

This upper temperature limit will; be set EXAMPLE I Twenty-five pounds of flaked sodium hydroxide were placed in a Werner-Pfleiderer type mixer of a capacity of 28 gallons, and equipped with a water jacket, an inlet pipe, an outlet pipe leading to a reflux condenser, and a thermometer The mixer is flooded with nitrogen to remove the air present. A total of 45 lbs. of a crude mercaptan mixture obtained as a by-prodnot from the refining of petroleum containing methyl mercaptan, ethyl mercaptan, propyl mercaptan, and various butyl meroaptans, sulfides, and other impurities, and boiling within the following range was then fed into the mixer:

Initial boiling point 30 33 20% 35 30% 37 40% 39 50% I 42 60% 45 70% 48 80% I I 54 90% 64 Finalboiling point 163 The rate at which the crude mixture of mercaptans was added was controlled so that the temperature was not allowed to exceed about 45 C. to 50 C. and required about 2 hours. After the addition of the mercaptan mixture was complete, the mixing was continued until the reaction was completed, as indicated by a drop in the temperature. This occurred in about one hour after the addition of the mercaptan. Forty-seven and one-half pounds of carbon disulfide were then slowly added, to the mixture, the rate of addition being adjusted so the temperature did not exceed45 C. to 47 C. This addition requiredabout 3 hours. The mixing was then continued for another 3 hours, at the end of which the temperature had dropped to 30 to 33 0., indicating the completion of the re-,

action. This product was a solid, and was found to be valuable as a flotation reagent for the concentration of mineral ores without further purification or refining.

EXAMPLE II .Twenty-fiveparts by weight of crudev mercaptan mixture described in Example I and 30.5 parts by weight of carbon disulfide were mixed together in a reaction vessel provided with a reflux condenser and stirring the reaction mixture. Sixteen parts by Weight of powdered sodium hydroxide was added to the reaction mixture in small portions at short intervals. The

' and was found to be a valuable flotation reagent.

EXAMPLE III Thirty-seven parts of the crude mixed mercaptans described in Example I, and 43 parts of carbon disulfide were mixed together. Twentytwo and one-half parts of sodium hydroxide in a 40% aqueous solution was then added slowly with stirring. The reaction mixture was .cooled to avoid vigorous reflux of the volatile. components of the reaction mixture. After the caustic Ill solution had been entirely added, the reaction mixture was a thick, pasty, yellow mass. This. mas s was then centrifuged and dried to obtain 68parts: by weight of the product which was a valuable flotation reagent.

EXAMPLE IV Ten parts by weight of an aliphatic mercaptan cut boiling within the range of about 70 C. to about 94 C. secured by the fractionation of a crude mixture of. mercaptans obtained as a byweight of sodium monoxide were thoroughly adi mixed together until all particles of the sodium this new flotation reagent.

the flotation of many types of ores and findsgenwhatever loss. may occur due to decomposition during the. flotation operation.

monoxide were broken up andhad disappeared. Tenparts by weight of, carbon disulflde were then added to the reaction mixture and the stirring continued. Reaction was indicated by a rise in temperature and by the reaction mass turning yellow. At the end of the reaction, as indicated by a dropi in temperature, a thick pasty mass remained, which set up to an apparently dry solid on standing. Fourteen parts by weight of the product were recovered, which consists principally of a mixture of sodium butyl trithiocarbonates, with the impurities either in their original or reacted form.

EXAMPLE V Fourteen parts by weight of a fraction of a crude mixture of aliphatic mercaptans secured as a by-product of the refining of petroleum,

; boiling within the range of 20 C; to 40 C. were addedslowly with cooling to 3;? parts by weight of metallic sodium. Twelve parts by weight of carbon disulfide were then added and the mixturethoroughly agitated with suflicient cooling to keep the temperature belowthe reflux tempereral application, forexample, in the frothgflotation of metallic sulfide ores for the concentration of lead, copper, zinc, gold, silver, etc.

While this reagent has great selective action or collecting action in the froth flotation of sulfide minerals in the flotation operation, it does nothave substantial frothing properties, so that anappropriate frothing agent, such aspine oil,

should be employed in conjunction therewith incarrying out the flotationoperation. In carrying out the flotation operation, itis preferable to use either an alkaline or a neutral circuit depending upon the character of the ore. acid circuit the various alkyl trithiocarbonate salts contained in this reagent have a tendency to}instabilityydepending upon the acidity of the circuit and the particular compound. Aslightly acid circuit canibe successfully used, however; if suflicient reagent, is added to compensate for Twenty-four parts by In an Theamount of th'eflotationreagent in accordance with, this invention, which will be used in froth flotation will depend upon the particular ore being treated. Ordinarily, it will be found that the optimum amount. will be within the range of about 0.02 lb. to about 0.7 lb. per ton of dry. ore feed, and usually within the range of about. 0.05 1b.: to about 0.5 lb. per ton of dry ore feed. i

The froth flotation of minerals utilizing my new flotation reagents as a collector, will be more specifically illustratedby the examples which follow: i

i i EXAMPLE VI Matahambre copper ore from Santa Lucia, Cuba, containing chalcopyrite and pyrite in a. shale gangue and analyzing 4.7% copper, 17.8% iron and 46.8%;insoluble matter was tested in a copper circuit as, follows: It was prepared in a 50% pulp in water by crushing 1015 grams of the ore to pass 8 mesh, admixing with an equal weight of tap water and then grinding in a ball mill to a finenessof greater than 48 mesh. Two thousand grams of this pulp were then transferred Table. 1.

Percent 011 percent Cu percent weight assay distribution Concentrate 20.7 22.9 92.2 Tailing .i. 79.3 i 0. 51 7. 8 Heads 100.0 5. 15 100i To obtain a comparison with curre nt plant practice, using a well known and widely used flotation reagent the above procedure was repeated, with the substitutionof pentasol xanthate for the flotation. reagent made in accordance with this invention. Using pentasol xanthate as. the flotation reagent, the following results were. obtained:

i Table i 2 Percent; Cu percent Cu percent weight assay distribution Concentrateunt 19. 7 22. 7 92. 0 Tailing. 80. 3 0. 48 8. 0. Heads .i 100. 0 5. 100. 0

A comparison of i the data of Tables 1 and 2 shows clearly that the flotation reagent made in accordance with this invention showed a better.

copper recovery than the widely used pentasol xanthate when tested under exactly comparable conditions. In considering theseresults it will be fully appreciated that an increase of a few tenths of a per cent in the amount of metal in- A sample of St. Joseph Balmat zinc ore, from Balmat, N. Y., which is a mixture of metallic sulfides of lead, zincand iron (galena, sphaleritemaramatite, pyrite) in. a. siliceous-dolomitic. gangue, and which analyzed 0.23% Pb,;8 .-3%.\Zn,

17.4% Fe and 30.3% insolubles, was subject'ed to froth flotation in a zinc circuit by the following procedure: 7 One thousand and six grams of this ore were crushed to pass 8 mesh, admixed with an equal weight of tap water and then ground in a 'ball mill to a fineness of minus 48 mesh. Two thousand grams of the resulting minus .48 mesh pulp was then transferred to a 1000 g. Denver Sub-A Fahrenwald type flotation machine (impeller speed 1800 R. P. M), and further diluted to 20% solids. To this pulp was then added per ton of dry ore 0.06 lb. of sodium cyanide, 2.00 lbs. of lime and 1.4 lbs. of copper sulfate, and the pulp conditioned by agitation for Table 5 Percent Zn percent jZn percent weight assay distribution Concentrate 24. 9 50.0 96.0 Tails 75. l 0. 53 4. Heads 100. 0 12.8 100.0

For comparison approximating plant practice on this ore, the above procedure was repeated using 0.16 lb. of potassium ethyl xanthate instead of the same amount of the flotation reagent made in accordance with this invention, with the results shown in Table 6.

ten minutes. After the conditioning was completed 0.10lb. of the flotation reagent prepared Table by the procedure of Example I and 0.15 lb. of

pine oil was added. Frothing for minutes Percent n percent p e yielded theooncentrate-and tailing as shown in weght assay dsmbutm We Table 3 Percent Zn percent Zn percent g t assay distribution A comparison of the data of Tables 5 and 6 shows that again the flotation reagent in accord gg ggg 2 8- ance with this invention gave a concentrate conneadsjjjjiiiiiiijiIIIZIZjI 10010 7:89 .1000 ain ne a hi her p r nta e of zinc than ha obtained using potassium ethyl xanthate.

. To secure a comparison approximating plant EXAMPLE IX practice for this ore, the above procedure was repeated with the substitution of 0.10 lb. of potassium ethyl xanthate for the flotation reagent made in accordance with this invention, with the results shown in Table 4.

Table 4 Percent Zn percent Zn percent weight assay distribution Concentrate 17. 0 44. 5 92. O Tails 83.0 0.83 8.0 Heads 100.0 3.25 100.0

A comparison of the data of Tables 3 and 4 shows that the flotation reagent in accordance with this invention collected a concentrate containing ahigher percentage of zinc than the ethyl xanthate did, and thereby is a more efficient collector than ethyl xanthate in the flotation of zinc ores.

EXAMPLE VIII St. Joseph Edward's ore, from Edwards, N. -Y.,

is similar to the Balmat concentrated in Example VII in beinga massive sulfide with substantially the same gangue minerals but without alteration products. The zinc therein occurs as sphalerite ZnS. A sample of this ore which analyzed 11.8% Zn, 8.0% Fe, 16.1% CaO and 3.1% insolubles was prepared as a pulp containing 50% solids following the same procedure described in Example .VII, except that the ore was ground to a minus 35 mesh. Two thousand grams ofthis pulp were then placed in a 1000 gram Denver Sub-A Fahrenwald type flotation machine and further diluted to 20% solids. This .-pulp.was then conditioned by ten minutes agi- "tation after the addition per ton of dry ore of 5.5 lbs. of lime and 1.4 lb. of copper sulfate, after which 0.16 lb. of the flotation reagent prepared by the procedure of Example I and 0.22 lb.

Midvale lead ore from Midvale, Utah, is a high grade sulfide ore containing lead as galena, zinc as sphalerite and iron as pyrite and analyzes 17.8% Pb, 9.1% Zn, 10.8% Fe, and 31.4% insolubles. A sample of this ore was subjected to flotation in a zinc circuit by the following procedure: One thousand grams of this ore were made into a 50% pulp with tap water, ground to a fineness of minus 48 mesh and placed in the flotation machine and diluted to 20% solids, as in the preceding examples. To this pulp was then added per ton of dry ore 0.40 lb. of the flotation reagent prepared by the procedure described in Example 1. 1.0 lb. of zinc sulfate, 1.0 lb. of sodium sulfate, 0.43 lb. of coal tar creosote and 0.19 lb. of pine oil. The pulp was then frothed for 10 minutes yielding the concentrate. and tailing as shown in Table 7.

Table 7 Percent Pb percent Pb percent weight assay distribution Concentrate 34. 6 3. 6 75. Tai 65. 4 7. 05 25. Heads 100.0 I 18.3 100.

To obtain a comparison approximating plant procedure for this ore the above test was duplicated with the substitution of 0.401b. of potassium ethyl xanthate for the flotation reagent of this invention. The results given in Table 8 were obtained:

A comparison of the data of Tables 7 and 8 shows the flotation reagent in accordance with this invention to be more eflicient than the. widely used potassium ethyl xanthate for the COO scribed and claimed is in no Way limited thereby.

flotation of lead ores. Thus, it will be observed that both the percentage of lead in the concen trate (Pb per cent assay) and the per cent of total lead recovered in the concentrate (Pb per cent distribution) was higher when my new flotation reagent was used than when potassium ethyl xanthate was used.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention asherein broadly de- This application is a division of my copending application Serial No. 153,064, filed July 10, 1937.

What I claim and desire to protect byLetters Patent is:

1. In a process for the concentration of sulfide ores and sulfide minerals, by froth flotation, the step which comprises subjecting the ore in the form of a pulp to froth flotation in the presence of a flotation reagent consisting of the reaction product of an alkali metal hydroxide, carbon disulphide and a crude mixture of organic sulfur compounds rich in alkyl mercaptans but contain ing a minor amount of non-mercaptan organic sulfur compounds, the said crude mixture being that by-product of petroleum refining obtained by steam blowing the extract resulting from the treatment of the petroleum in an aqueous alkali solution, the said reaction product, comprising a mixture of alkali metal mono-alkyl trithiocarbonates and organic sulfides, disulfides and more complex sulfur compounds.

from. the treatment of the petroleum in an aqueous alkali solution, the said reaction product, comprising a mixture of alkali metal mono-alkyl trithiocarbonates and organic sulfides, disulfides and more complex sulfur compounds.

3. In a process for the concentration of sulfide ores and sulfide minerals by froth flotation, the

step Which comprises subjecting the ore in theform of a non-acid pulp to froth flotation in the presence of a flotation reagent consisting of the reaction product of a sodium hydroxide, carbon disulfide and a crude mixture of organic sulfur compounds rich in alkyl mercaptans but containing a minor amount of non-mercaptan organic sulfur compounds, the said crude mixture being that by-product of petroleum refining obtained by steam blowing the extract resulting from the treatment of the petroleum in an aqueous alkali solution, the said reaction product, comprising a mixture of sodium mono-alkyl trithiocarbonates and organic sulfides, disulfides and more complex sulfur compounds.

EMIL O'I'T. 

